Gearless differential speed reducer structure

Abstract

Gearless differential speed reducer comprising a first disc secured to a casing, a second rotary disc arranged to face the first disc, sinuous grooves provided with the facing sides of discs, the sinuous shapes of which are epicycloid and hypocycloid curves determined along a certain pitch circle, spherical balls provided between the discs to position into the grooves, and an eccentric shaft connected to the rotary disc through a bearing. Rotational movement of the eccentric shaft allows the rotary disc to rotate around one end of the shaft, while going along the pitch circle, since the balls rolls along the sinuous grooves. A single rotation of the shaft permits the rotary disc to travel by the length equivalent to that of two lobes of the grooves, yielding speed reduction ratio as a formula of 2/N(N+2) when the groove of the first disc counts its number of lobes as N.

What is claimed is: 
     
       1. A gearless differential speed reducer structure comprising: a crank-shaped eccentric shaft having input and output ends, and disposed to receive a rotary movement;   a second disc fixed to a stationary member in a manner to rotationally admit said eccentric shaft through a central hole provided within said second disc;   an epicycloidal-related groove provided on a facing surface of said second disc to run continuously along a predetermined circle with a single wave as a lobe;   a first disc rotationally mounted on said output end of said eccentric shaft through a bearing to adjacently face said surface of said second disc;   a hypocycloidal-related groove provided on a facing surface of said first disc to run continuously along a predetermined circle with a single wave as a lobe;   both said grooves being recessed in a direction perpendicular to the surface of said discs and having two opposed side walls of the same height and the width of each groove being uniform through the lobes thereof;   rollable balls located on the groove of said first and second discs with the spherical surfaces thereof always contacting the walls of each groove and rolling along the grooves thereof upon actuation of said eccentric shaft, converting rotary movement of said first disc into a rotation component and a revolution component;   a rectifier disc rotationally mounted on a shaft to face another surface opposite the grooved surface of said first disc so as to provide a speed reduction output;   a rectifier means provided between said first disc and said rectifier disc to absorb the revolution component of said first disc and to transmit only the rotational component to said rectifier disc; and   the difference between the number of lobes of said first disc and that of said second disc being two.   
     
     
       2. Gearless speed reducer structure as recited in claim 1 comprising: annular grooves provided within said first disc and said rectifier disc and having a diameter corresponding to the eccentricity of said eccentric shaft, and rollable balls positioned into said annular grooves.   
     
     
       3. Gearless speed reducer structure as recited in claim 1 comprising; a circular concavity provided within said first disc and said rectifier disc disposed to face each other and having a diameter corresponding to the eccentricity of said eccentric shaft, and rollable balls positioned into said annular grooves.   
     
     
       4. Gearless speed reducer structure as recited in claim 1 comprising: projections provided within said rectifier disc;   circular concavities provided within said first disc to admit said projection thereinto having a diameter corresponding to the eccentricity of said eccentric shaft.   
     
     
       5. Gearless speed reducer structure as recited in claim 1 wherein said rollable balls are made of wear-resistant ceramics. 
     
     
       6. Gearless speed reducer structure as recited in claim 1 wherein a rotary disc is provided to face against said first disc, with the facing sides of said rotary and first discs having cycloidal grooves along a predetermined circle within which rollable balls are placed.